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04:08, 17 October 2012 {{Mercerization}}
'''Mercerization''' is done to provide [[cotton]] a higher gloss and more strength, also to increase its absorption properties. It is also quite important to in order to reduce shrinkage after wash. Mercerization triggers and smoothens rough, mechanical stretches in the material as a result from spinning and weaving. Therefore, it will improve the smoothness after washing and at the same time the shrinkage will decrease. Mercerization is performed on special machines in strong [[caustic soda]] (20%). The fabric is generally not allowed to shrink freely and is held extended by chains. Swelling in the caustic soda is usually performed cold. Treatment in liquid [[ammonia]], which swells cellulosic materials, has a similar effect on cotton fabrics.
A good wetting of the fabric is a prerequisite for the mercerization to success and this is why special wetting agents for mercerization have been developed. After that the swelling has passed the fabric is usually put in a steam box and later rinse bins for washing and removal of alkali. The most concentrated rinse tanks are either concentrated by evaporation or are reconfigured by more alkali to be re-used in the mercerization. The more soluble of solutions can be partially reused in bykning and washing. A related concern is the pollution that is dissolved out of the cotton in mercerizing and that puts limits on the amount of the mercerizing accounts that can be reused.
==Dry mercerization==
Recently a new form of mercerization has been used called dry mercerizing. In this method, the fabric is impregnated with a fixed amount of sodium hydroxide and is then dried on stent-frames. Later it is washed and de-acidified in the usual way. Dry mercerization does not provide the same shine and strength as the normal mercerization.
==Environmental Facts - mercerization==
The mercerization mass is quite concentrated (20%) and therefore attempts have been made to reuse it. This is done partly by cleaning dirty baths, and by evaporating relatively concentrated rinse baths. More dilute rinse baths can be used for bleaching and if bleaching is done after mercerization the residual alkali left in the garment can be ignored. The mass only residues after neutralization is salt. At mercerization the mass must have good wettability and therefore some special surfactants are added, which must be able to withstand high alkali concentrations. To protect the cotton fiber (only cotton is mercerized) against oxidation so-called fiber-protective solutions are added. Environmental information on these special solutions must be sought from the suppliers.
==BAT (Best Available Technique) – mercerization==
[[BAT]] provides recovery of mercerization closed. This is currently done without any major problems up to a level of recovery that is dependent on the purity of the fabric mercerized. In turn this limits the mercerization process to recover “raw weave”. The recycling of the mass is mostly dehydrating mass-solutions, and therefore a concentration of impurities. So far there are no economically viable processes for the recovery of mercerization masses where both inorganic and organic contaminants can be removed.
==Sources==
[[Textile Environmental Handbook]]